Control apparatus for compressors



Oct. 2, 1928.

1,685,781 L. F. HOFFMAN CONTROL APPARATUS FOR COMPRESSOR:

Filed Feb. 8, 1927 2 Sheets-Sheet 1 I lllllwl l/VVEN TOR. Leo/7 Hoff/776W A HOR E).

Patented Oct. 2, 1928.

UNITED STATES 1,685,781 PATENT OFFICE.

LEON F. HOFFMAN, OF FRANKLIN, PENNSYLVANIA, ASSIGNOR TO CHICAGO PNEU- MATIG TOOL COMPANY, OF NEW YORK,

N. Y., A CORPORATION OF NEW JERSEY.

CONTROL .APPARATUS FOR COMPRESSORS.

Application filed February This invention relates to fluid compressors or pumps, more particularly air and gas compressors, the output of which is arranged to be varied automatically in response to the demands upon the receiver into which the compressed fluid is discharged. For ellicient and economical operation it is customary to arrange such machines to unload in a plurality of stages, as three stage (full load,

I half load, no load) or five stages (full load, three quarter load, halt load, quarter load, no load).

One object of the present invention to improve the control and regulation of multilfi stage compressors. Another object is to provide simplified and positively acting apparatus for this purpose. Another object is to permit convenient adjustment oi? the range of operation of such apparatus. Other objects will be apparent from the detailed description which follows:

In order to illustrate the invention and the manner of operation one concrete embodiment thereof is shown in the accompanying drawings in which:

Fig. l is a fragmentary and somewhat diagrammatical view of a variable volume compressor equipped with regulating apparatus in accordance with the present invention Fig. 2 is an enlarged side elevational View partly in section and partly broken away of the fluid pressure governor or regulating ap-" paratus Figs. 3 and 4 are respectively side eleva- 35 tional and end elevational views of details of the regulating apparatus.

In Fig. 1 a variable volume compressor 18 indicated'at A arranged to be controlled by a fluid pressure governor or regulating apparatus at B. Compressor A has unloading devices 0, (Z, c and f arranged to be operated in the order given. Unloading devices and (Z control clearance pockets 0. and a? so that the compressor is adapted to be unloaded in 45 five steps. WVhen none of the unloading de vices is actuated the compressor operates at full load. On actuation of unloading device 0, first stage unloading occurs and the left end of the compressor is half unloaded so 50 that the compressor operates at load. On

operation of the unloading device (l, the opposite or right end of the compressor is half unloaded and the entire compressor operates at half: load. On operation of unloading t.

vice e,- the left end is entirely unloaded nlhl 8, 1927. SerialNo. 166.624.

the compressor operates at quarter load. When device f is actuated the entire compressor is unloaded and operates at no load.

The loading of the compressor in stages is in the reverse order.

The fluid pressure governor is shown in complete detail in Figs. 2, 3 and 4. The governor comprises a casing 5 providing a chamber 6 in which is disposed a diaphragm 7. providing a small chamber 8, having a connection 9 to the air receiver. Pressure fluid admitted to chamber 8 acts through diaphragm 7 upon a lever arm 10 pivoted at 11 and provided. at its outer end with weights 12. Movement of lever 10 is transmitted through a yoke 18 to an arm or link from which is suspended a fluid. control or pilot valve 15 of the Mason regulator-type controlling passages 16 and 17 leading to opposite ends of a chamber in which reciprocates a piston 18. The fluid controlled by valve 15 may be water under pressure admitted at 19 and arranged to drain away at 20. Piston 18 is connected by head 21 and rod 22 to a balanced piston 23 movable in a cylinder 23. The space between the heads of piston 23 is always in communication with receiver pressure through an inlet pipe 24. Movement of piston 23 to the right serves to connect to receiver pressure in succession pipes 25. 26, 27 and 28 which lead to the unloading devices and effect respectively, first stage, second stage, third stage and fourth stage, or totally unloading stage. An additional pipe 29 beyond the limit of movement of piston 23 communicates with atmosphere and serves as a vent.

. In order to ensure that the movement of pistons 18 and 23 shall be controlled in well defined steps to produce the progressive stages of unloading and loading of the com-' pressor, compensating means are provided quickly to restore pilot valve 15 to neutral position after movement. To this end movement of piston 18 is transmitted by a head 30 to a rack bar 31, the teeth of which mesh with a pinion 32 secured to an eccentric rotatable cam 33 having spaced depressions 33 in its periphery. A roller 34 carried by the lower arm of a bell crank 35 is maintained in contact with the periphery of cam 33 through the action of a spring 36. The upper arm of bell. crank 35 is connected by a link 37 to the depending arm of a bell crank 38, the upper arm of which has pivotal connection with link 14. g

loo

compressor. rotated untll roller 3-1l has reached the first depression 33 111 the peripheryot the cam.

The operation of the fluid pressure control apparatus as so far described is as iollows. hen the pressure against diaphragm 7 becomes sufiicient to overcome weights 12,- lever 10 moves upwardly carrying with it the yoke 13 and the link 14, thus lifting pilot valve 15 which uncovers the upper, and lower passages 16 and 17, thus admitting water against the left end of pistonlS and at the same time venting the water from the opposite side of the piston. In consequence piston. 18, as well as, piston 23 and rack bar 81 connected there toinov e to the right and the unloading piston 23 connects pipe 25to receiver pressure effecting the first stage of the unloading of the Meanwhile cam has been The cam has rocked valve crank 35 to the left and this inoven'ient has been com1nuni cated by link 37 to bell crank 38 which has depressed. link ll and restored pilot valve 15 to "its original neutral position so that the unloading mechanismhas come to rest after su'lficient movement to etl'ect first stage unloading of the compressor. -Upon further increase in pressure in the receiver the next v position of the unloader piston is assumed with pipe26 uncovered and eilecting second stage unloading of the corn ressor. Upon further increases in pressure the remaining pipes 27 andv 28 are uncovered in succession in" an obvious manner. Upon a drop in pressurethe unloading steps are rctraced inorder to effect progressive loading of the compressorl i i Means are provided for producing a dampening effect upon weight lever 10 the more positively to fix the extento'f each movement of piston 18 and for adjustably varying the range of operation of the regulating apparatus, such means being directly associated with the co:upe nsating mechanism v0t the regulating apparatus. A iixcd arm 39 extending from casing 5 and has a depending portion 39 upon which is pivotally mounted .a bell crank 40 or its equivalent. The hori-' zontal arm of hell crank 10 supports a hollow I casing 41 receiving therewithin in telescoping' engagement plunger rod 12 whiclris maintained in yield ng contact with lever 10 by a spring 43, the tension of which is ad IEO! iston 18 and conseouentl i for the rim loader piston 23. The dillcrc-nce in air pres sure necessary to cause n'iovcinent ol' pistons 18 and'23 from one definite position to the nextin unloading the compressor may be'variedby securing the left end oflink 4-1 inn diifercnt hole e0 in the depending arm of hell crank lO. Assuming the difierence in air pressure at which the successive movements of the piston occur is approximately three pounds,changing the rod'to a hole' lO nearer the pivot of hell crank 40 increases the range betweenthe successive steps and changing it to a hole 10 more remote-irom the pivot decreases the range or pressure ditlerential. Such changes in the connection between link 46 and member 4E0 vary the angle of incidence of plunger 42 relative to lever 10.

From the above it will be apparentthat the present invention provides automatic, positively operating mechanism for governing the unloading ot a compressorm well defined steps or stages, that the improved form of compensating mechanism permits a more compact construction than has heretofore been possible, and that the dampening and range adjusting means in cooperating withthe compensating mechanism insures accurate functitming o1"; the regulating apparatus and permits flexible and convenient control of the operating range or pressure differential between the steps or stages of unloading and loading. i A

While a single cylinder compressor only has been shown in Fig. 1 merely for illustrative purposes, it is obvious that the principle of operation ofthe invention adapts the same for the automatic control, in any desired number oi" loading and unloading steps, of varied types and arrangen'icnts of COlTlPlCSSlDg equipment whether single or multiple cylinder, or whether single acting, double acting, duplex, compound, or compound duplex. The regulating apparatus has been shown in what is now considered to be a preferred form but is obviously capableojt' modification and variation withoutdeparting from the spirit of the invention. It is accordingly to be understood that the invention is not limited to the specific details of arrange ment .and form herein shown and described, but covers all changes, modifications and adaptations within the scope of the appended claims.

I claim as my invention:

1. In a pump or compressor, the combination with a cylinder and a plru'ality of urneccentric cam arranged pilot valve to neutral position after each' movement, and means including a rotatable member for actuating said first-named means.

2. In a pump or compressor, the combination with a cylinder and a plurality of mi loading devices arranged to unload the cylinder in whole or in part, of automatic regulating apparatus for controlling said unloading devices comprising a pilot valve controlled by receiver pressure, means for returning the pilot valve to neutral position after each movement, and means including an eccentric cam for actuating said first named means.

3. In a pump or compressor, the combination with a cylinder and a plurality'of unloading devices arranged to unload the cylinder in well defined steps, of automatic regulating apparatus for controlling said unloading devices comprising a pilot valve controlled by receiver pressure, a rociprocable piston controlled by said valve, means for returning the pilot valve to neutral position after each movement, and means'for actuating said first named means comprising a rack member arranged to be moved as a result of the movement of said piston, and a stop member actuated by said rack member.

4. In a pump or compressor, the combination with a cylinder and a plurality of unloading devices arranged to unload and load the cylinder in Well defined steps of automatic regulating apparatus for controlling said unloading devices comprising a pilot valve controlled by receiver pressure, a reciprocable piston controlled by said valve, means for returning the pilot valve to neutral position after each movement, and means for-actuating said. first named means comprising a rack member arranged to be moved as a result of the movement'of said piston, and an for rotation by said rack member. a

5. In a pump or compressor, the 'combina tion with a cylinder and a plurality of unloading devices arranged to unload and load the cylinder in well defined steps, of automatic regulating apparatus for controlling said unloading devices comprising a pilot valve controlled by receiver pressure, means for returning the pilot valve to neutral position after each movement, means including a rotatable member for actuating said first named means, and means for adjusting the operating range of said apparatus.

6. In a variable capacity compressor, the combination with a cylinder and a plurality of unloading devices arranged to unload. and load the cylinder in well defined steps, of automatic regulating apparatus for controh ling said unloading devices including a pilot valve controlled by receiver pressure, compensating means for returning said pilot valve to neutral position aftereach movement and means associated with said compensating.

means for controlling the operating range of said apparatus.

7. In a variable capacity compressor, the combination with a cylinder and a plurality of unloading devices, arranged to unload the cylinder in well defined steps of automatic regulating apparatus for controlling said uncombination with a cylinder and a plurality of unloading devices arranged to unload and load the cylinder in Well defined steps, of automatic regulating apparatus for controlling said unloading devices comprising a weighted arm movable in response to receiver pres- .sure, a pilot valve movable in response to movement of said arm, compensating means for returning said pilot valve to neutral position after each movement, means arranged to offer resistance to the movement of said arm in one direction, and a connection to a portion of said compressor for the purpose of controlling the operating range of said apparatus.

9. In a variable capacity compressor, the combination with a cylinder and a plurality of unloading devices arranged to unload the cylinder in well defined step-s, of automatic regulating apparatus for cont-rolling said unloading devices comprising a weighted arm movable in response to receiver pressure, a pilot valve movable in response to movement of said arm, compensating means for returning said pilot valve to neutral position after each movement, and means arranged yieldingly to resist movement of said arm in one direction, said lastnamed means having an adjustable connection to a fixed portion of said compressor adjustably to control the operating range of said apparatus.

10. In a variable capacity compressor, the combination with a cylinder and a plurality of unloading devices arranged to unload and load the cylinder in well defined steps, of am tomatic regulating apparatus for controlling said unloading devices comprising a we1ght ed arm movable in response to receiver pressaid pilot valve to neutral posit-ion after each.

sist movement of theilatter, and means including'a connection-to said plunger means for changing'the angle of said plunger 'relative to -said arm thereby adjustably to control the operating range of said apparatus.

11. In avari-able capacity compressoiythe combination With 'a cylinder having a plurality of unloading devices, oi automatic reg lating apparatus for controlling said unloading devices comprising a Weighted arm movable in response to receiver pressure, a pilot valve movable in response to movement of said arm, compensating means for return ing said pilot valve to neutral positionaitcr each movement, means including a spring pressed. plunger mounted abovesaidarm to resist upward movement of the latter, and means establishing a connection between said plunger and said compressor whereby the angular position of said plunger relative to said arm determines the operating range of .said apparatus.

12. In a'variable capacity compressor, the combination Witha cylinder having aplurality of unloading devices, or? automatic regulating apparatus for controlling said unloadingdevices comprising a Weighted arm movable in response to receiver pressure, a pilot valve movable in response to movement of said arm, compensating means for returnvalve movable in response to movement of said arm,compensating means for returning movement, and means comprising a support, a plunger engaging said arm dingly to resist movement of the same, a pivotal mounting for said plunger on said support, and a link connection for said mounting for controlling the operating range ofsaid apparatus.

14. In avariable capacity compr or, the combination with acylinder having a plurality of unloading devices, of automatic regulating apparatus forcontrolling said unloading devices comprising a Weighted arm movable in response to receiver pressure, a

pilot'valve movable in response/to "movement of said arm, compensating-means for returning said pilot valve to neutral position after each movement, and means comprising a support, a plunger engaging said arm yieldingly torresist movement on; the same,- a pivotal 15. A fluid-pressuregovernor for a variable,

volumecompressor comprising a fluid control valve, means for eilectmg movement of said valve in response to VAIHIUOIIS'IH pressure, a

movable member controlled by said valve,-

means for returning said valveto neutralposition after each movement to cause said menr her to advance or recede invvell defined-steps, and means for varying theoperating range of the governor and-the pressure differential between the steps of said member.

16. A fluid pressure governor-for a variable volume compressor comprising afiuid control valve, means for effecting movement of said valve in response to variations in pressure, a movable member controlled by said valve, compensating meansactuatcd by movement of said member for returning said valve to neutral positi on after each movement, mechanism cooperating with said compensating means positively todetermine the extent of each movement of said member, and means "for varying the operating range ofthe governor and the. pressure differential between movements of said member.

17. A fluid p-ressuregovernorfor a variable volume compressor comprising a fluidcontrol valve, means for effecting movement of said valve in response to variations in pressure, a movable member controlled :by said valve, compensating means actuated by movement of said member for returning said valve to neutral position after each movement, mechanism cooperating with said compensating means positively to determine the extent of each movement of said member, and'means for adjusting said mechanism to vary the pressure difierential between any successive movements of said member.

18. The combination with a fluid control valve and movable member-controlled thereby, ofmeans -for returningthe valve to neutral position after movement, said 'means including a rotatable member arranged to fix the movement of said movable member at each action of the valve. A

19. The combination with a fluid control valve and a movable member controlled thereby, of-means for returning the valve to neutral position after movement, said means includ mg an eccentric rotatable-member arranged to oomitantly with the movement of said movperiphery arranged to fix the movement of able member. said movable member at each action of said 21. The combination With a fluid control valve, and rack and pinion means operated by 10 valve and a movable member controlled theresaid movable member for rotating said cam. 5 by, of means for returning the valve to neutral Signed by me at Franklin, Pennsylvania,

position after movement, said means includthis 4th day of Feb., 1927. ing an eccentric cam having depressions in its LEON F. HOFFMAN. 

